Designing 3-D molecular stars.

We have explored in detail the potential energy surfaces of the Si(5)Li(n)(5-6) (n = 5-7) systems. We found that it is feasible to design three-dimensional star-like silicon structures using the appropriate ligands. The global minimum structure for Si(5)Li(7)(+) has a perfect seven-peak star-like structure. The title compounds comprise, essentially, the Si(5)(6-) ring interacting with lithium cations. The ionic character of the Si-Li interactions induces the formation of a bridged structure. Concomitantly, our calculations show that the reduction of the Pauli repulsion and the maximization of the orbital contribution are also significant for the star-like structure formation. Additionally, the MO analysis of the systems suggests that the role of the lithium atoms is to provide the precise number of electrons to the central Si(5) unit. This is confirmed by the magnetic properties, which show that electron delocalization enhances the stability of the star-like structures proposed here.